Local area networks (LANs) and IP networking are well known in the art. LANs and IP networking in general and in particular relevant aspects of IP routing and ARP are described in the following publications:
International Standard for MAC Bridging: Std 802.1D, IEEE, 1993,
Virtual LANs (VLANs) standard: 802.1Q, IEEE, 1998,
LANE Standard: LAN Emulation Over ATM Version 2--LUNI Specification, af-lane-0084.00, ATM Forum, July 1997, available over the Internet at www.atmforum.com,
MPOA standard: Multi-Protocol Over ATM Specification v1.0, af-mpoa-0087.000, ATM Forum, July 1997, available over the Internet at www.atmforum.com,
"Layer 3 switches", InfoWorld magazine, Jun. 1, 1998 (Vol. 20, Issue 22), available over the Internet from www.infoworld.com,
the following Internet RFC documents, which are available over the Internet from, for example, the IETF home page at www.ietf.org: IP--RFC 791 ("Internet Protocol"), ARP--RFC 826 ("Address Resolution Protocol"), RFC 1812 ("Requirements for IP version 4 Routers"), RFC 1700 ("ASSIGNED NUMBERS"), RFC 1256 ("ICMP Router Discovery Messages"), SNMP--RFC 1157 ("Simple Network Management Protocol"), RFC 1213 ("Management Information Base for Network Management of TCP/IP-based internets: MIB-II"), VRRP--RFC 2338 ("Virtual Router Redundancy Protocol") and HSRP RFC 2281 ("Cisco Hot Standby Router Protocol").
Most routing-switches/switch-routers/layer-3-switches known today follow the same network architecture principles as traditional routers, in the sense that each switch is a routing entity, running routing protocols and requiring the configuration and maintenance of a router. If such layer 3 switches are installed centrally only in some locations in the network, while the rest of the network switches are layer 2 only, then the performance of layer 3 forwarding is limited. In order to achieve a distributed layer 3 switching system, such that the function of layer 3 forwarding is done in the most appropriate point in the network, this design calls for many or all of the network switches to be layer 3 switches. This requires the configuration and maintenance of multiple routing entities in the local area network, which is a significant configuration burden.
Some switching systems are designed around the concept of a central routing server with distributed layer-3 forwarding engines. These systems require a special protocol to communicate forwarding information between the routing server and the layer 3 forwarding engines. Some of these systems implement the MPOA standard for ATM networks. In Ethernet networks these protocols are proprietary requiring that the routing server and all layer 3 forwarding devices be from a single vendor, limiting the user's choice. Also, the introduction of such systems into an existing network requires a major change to the network.
Some ideas for layer 3 switching based on automatic learning of IP stations have been published. These are used by switches that front end a router to enhance its forwarding performance, and are not described as extended to network-wide distributed layer 3 switching systems. Such switches can perform layer 3 (IP) switching without being a router, i.e. without being known to stations as routers and without requiring the configuration that routers do. They assume the existence of a router in the network, use it as default forwarder and automatically learn information about IP stations.
The disclosures of all publications mentioned in the specification and of the publications cited therein are hereby incorporated by reference.